Furthermore, the present invention relates to a blind rivet having a mandrel and a blind rivet sleeve of this type, wherein the mandrel has a blind-side mandrel head for bearing in the region of a blind-side end of the sleeve shank, and also to a blind rivet connection of at least two workpieces using such a blind rivet.
Blind rivets are used for connecting workpieces where access is possible only from one side (the visible side). Here, the blind rivet is introduced with the blind-side mandrel head through pre-formed bores in the workpieces to be connected. This is followed by the setting or joining process in which the mandrel is pulled off on the visible side in the direction away from the workpiece arrangement (for example by means of blind-riveting tongs). This leads to a deformation of the head forming portion on the blind side and the formation of a blind head which bears against the blind-side workpiece surface after the setting.
The provision of a folding portion between head forming portion and sleeve head makes it possible to use the same type of blind rivet sleeve for different clamping thicknesses of workpiece arrangements (so-called multiple-region rivet).
On the other hand, it is preferable when setting blind rivets in plastics, such as, for example, thermoplastics, thermosets, CRPs, etc., to minimize the mechanical loading on faces and edges of the workpiece arrangement in the axial and/or radial direction.
The document DE 10 2010 017296 A1 discloses a blind rivet for connecting components made of plastic, which has a sleeve shank which has a first portion adjoining the sleeve head and a second portion adjoining the first portion. The second portion is designed as a head forming portion. The first portion has a higher strength than the second portion such that the outside diameter of the first portion does not increase or increases only slightly during the setting of the blind rivet.
As a result, it is intended to be possible to insert the first portion of the blind rivet into a workpiece bore with little oversize without a considerable radial pressing occurring between the rivet portion and the bore wall during the setting, by means of which the workpiece could be damaged.
Blind rivets of this type are used, in particular, in the motor vehicle industry in order to fasten attachment parts, wherein one of the workpieces or both workpieces can be produced from plastic.
In the case of blind rivet sleeves which have a folding portion, the sleeve fold thus formed in some clamping thicknesses can lead to high hole face bearing pressures and also to an expansion of the bore in plastic workpieces or even to the bursting of components particularly when small edge spacings are intended to be produced.
In order, for example when joining workpieces, to be able to design straps on the workpieces to be smaller, these edge spacings should be configured to be as small as possible.
Against this background, it is an object of the invention to provide an improved blind rivet sleeve for a blind rivet, a blind rivet having a mandrel and such a blind rivet sleeve and also a blind rivet connection of at least two workpieces using such a blind rivet, and it should be possible by means of the blind rivet to connect even softer or mechanically less loadable workpieces such as plastics while nevertheless achieving a relatively large clamping region.
In the case of the blind rivet sleeve stated at the outset, this object is achieved in that the sleeve head has in the region of the bearing face an axial recess for receiving at least part of the sleeve fold formed during the setting.
Furthermore, this object is achieved by a blind rivet having a mandrel and such a blind rivet sleeve, wherein the mandrel has a blind-side mandrel head for bearing in the region of a blind-side end of the sleeve shank, and also by a blind rivet connection of at least two workpieces using such a blind rivet.
The formation of an axial recess in the region of the bearing face of the sleeve head means that the sleeve fold which forms at least at certain clamping thicknesses can move at least partially into the axial recess during the setting. This makes it possible to achieve a situation in which the workpiece arrangement is not damaged during the setting process. In particular, a radial expansion of the rivet sleeve can be maintained within narrow limits. As a result, the edge spacing between sleeve shank outside diameter and inside diameter of the bore in the workpieces can be minimized. As a result, in turn, the outside diameter of the sleeve head can be minimized since a large hole covering of too large rivet holes for the purpose of tolerance compensation in the radial direction is not required.
Accordingly, the blind rivet can also be used, for example, in structural engineering with glass-fibre-reinforced plastics (CRPs), where high shear and tensile strengths are achieved.
Furthermore, if appropriate, high head tensile strengths can be achieved.
The object is thus completely achieved.